security: switch metadata to dynamic mbuf field

security: switch metadata to dynamic mbuf field

The device-specific metadata was stored in the deprecated field udata64.
It is moved to a dynamic mbuf field in order to allow removal of udata64.

The name rte_security_dynfield is not very descriptive
but it should be replaced later by separate fields for each type of data
that drivers pass to the upper layer.

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Haiyue Wang <haiyue.wang@intel.com>